The technical field of the invention is the control of charging of batteries of a motor vehicle, and more particularly the charging of such batteries at low temperatures.
The performance of a battery power, energy, durability) is very sensitive to operating temperature. At low temperature, the battery has less power, delivers less energy and is subject to degradation during charging, while at high temperature the battery has optimum performance in terms of power and energy.
The following documents are known from the prior art.
Patent application JP2001037093A discloses the use of a charge current oscillating at a frequency between 103 Hz and a few hundred Hz, with an amplitude of a few mV.
This teaching cannot be applied to Li-Ion batteries insofar as the specified frequency of 1 kHz is too high. In fact this frequency corresponds to the inductive part of the impedance spectrum, or the impedance of the metal parts (i.e. current collector) and electronic conductive compounds (i.e. conductive carbon). Furthermore, this patent application mainly describes the improvement at a constant voltage with a voltage oscillation of the order of a few mV, which improves the storage performance of the cell.
Document U.S. Pat. No. 7,227,336B1 determines the charging frequency of a battery from a diffusion coefficient.
Documents FR2943188, FR2964510 and FR2974253 disclose modulation of the battery charge current. However these documents do not provide any information concerning the effect of temperature on the choice of this frequency.
There is therefore a need for a system and a method for charging at low temperature which are optimized to reduce the charging time and the degradation of the battery during charging.